1. Technical Field
This invention relates to an electronic ID tag and a co-operating antenna. More particularly, it concerns an electronic ID tag including an identifiable data chip connected to an adjacent antenna, and a co-operating distant antenna. Between the adjacent antenna and the identifiable chip, and between the identifiable chip and a ground-plane plate are arranged impedance-matched inductances. The electronic ID tag may with advantage be placed in the threaded portion of a body, typically a drill pipe. The device is particularly suitable for identifying equipment which is used during work in a borehole, for example in the recovery of petroleum. The ID tag is well suited for positioning protected in the connecting box or pin of a drill pipe.
The term adjacent is used in this connection for details which are spaced less than 30 millimeters apart, whereas the term distant denotes distances of between 30 millimeters and 2 meters.
During drilling operations, for example as it is common in connection with the recovery of petroleum, a relatively great number of pipes are used, the pipes being screwed together into a pipe string. The pipe string may also include other equipment, for example controls and valve sections. A well of this kind is normally lined with casing in order to secure the borehole.
In order to keep track of the number of pieces of equipment and their physical condition, it has turned out to be useful to monitor the service time and stresses of the individual pipes and associated equipment, and also to keep track of the number and where the individual pipe is located in the pipe string.
2. Background Art
It is known for an electronic ID tag to be placed on the pipe or equipment, which is read manually by means of matched equipment when the pipe is run into the well and when it is pulled from the well. U.S. Pat. No. 5,142,128 thus discloses an apparatus for identifying equipment related to the recovery of oil, which is also arranged to keep track of the service time of the equipment. The document describes a hand-held reading device for electronic ID tags.
Electronic ID tags of the kind concerned here, are mounted on the outside of the pipes near the connecting means of the pipes. Thereby, the ID tags can be read when passing an antenna. This positioning entails that the ID tags are subjected to wear during the moving of the pipe in the borehole and to damage from, for example, power tongs during make-up and break-out operations. It has also turned out that the attachment of the ID tags in the pipes is adversely affected by relatively large pressure variations in the well.
Equipment according to prior art exhibits drawbacks related to applicability and/or reliability, as, among other things, the range of signals from the ID tags is relatively small, the ID tags are subjected to wear and may be damaged during the assembling of the pipes.